Heading over to Europe or other parts abroad? There are a lot of firms waiting to charge you exorbitant rates. Unless you know how to get a rented SIM or use Skype in all the right places, as this flowchart explains.

The graphic comes from a BBC article by NY journalism student Suemedha Sood, detailing all the ways you can call back home from your cellphone, laptop, internet cafes, or another phone with a rented SIM card. It's realistic, too, with at least one or two options ending up with "Call your mum when you get home." Keep it handy the next time you're lost in the world of roaming, unlocking, and SkypeOut credits.